Integrated fuel cell gas diffusion layer structure and preparation method thereof

Abstract

The invention provides an integrated fuel cell gas diffusion layer structure and a preparation method thereof. The integrated fuel cell gas diffusion layer structure comprises a fiber skeleton, and a macroporous layer and a microporous layer which are respectively arranged on two sides of the fiber skeleton, the preparation method comprises the following steps: S1, preparing a water repellent agent solution, macroporous layer slurry and microporous layer slurry; s2, immersing the fiber skeleton into a water repellent agent solution, mangling and drying; s3, coating one side of the fiber skeleton with the macroporous layer slurry, and drying; s4, coating the other side of the fiber skeleton with the microporous layer slurry, and drying to obtain an integrated diffusion layer semi-finished product; and S5, carrying out heat treatment on the semi-finished product. The conductive network is formed on the front side, the back side and the interior of the carbon fiber skeleton in the form of coating the carbon fiber skeleton on the front side and the back side of the carbon fiber skeleton without carbonization and graphitization treatment, the conductivity requirement of the fuel cell is met, the microporous layer has a uniform pore structure, and the gas diffusion capability of the fuel cell is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to an integrated fuel cell gas diffusion layer structure and its preparation method. Background Technology

[0002] With the continuous growth of global energy demand and increasing emphasis on environmental protection, the development of clean and efficient energy conversion technologies has become an urgent task. As a device that directly converts chemical energy into electrical energy, fuel cells have received widespread attention and shown great application potential in many fields due to their significant advantages such as high energy conversion efficiency and low pollutant emissions.

[0003] Among the many components of a fuel cell, the gas diffusion layer (GDL) plays a crucial role. The main functions of the gas diffusion layer include supporting the catalyst layer, conducting electrons, diffusing reactant gases, and discharging water generated in the reaction. Its performance directly affects the overall performance and stability of the fuel cell. In particular, the microporous layer (MPL) in the gas diffusion layer plays a key role in gas diffusion, mass transfer processes, and water management.

[0004] Traditionally, microporous gas diffusion layers are often tightly integrated with the catalyst layer or designed and fabricated as an integral part of the gas diffusion layer. However, this structure has many limitations. For example, when the microporous layer is damaged or its performance needs to be optimized separately, it cannot be replaced and adjusted independently, which limits the further improvement of fuel cell performance. In addition, the fabrication process of traditional microporous layers is often complex, costly, and difficult to achieve precise control over the microporous structure and performance.

[0005] In existing technologies, to improve the drainage capacity of the gas diffusion layer, the microporous layer is made into a gradient double microporous layer structure, thereby improving the drainage capacity of the gas diffusion layer. However, although this method can improve the drainage capacity to a certain extent, the base layer still experiences varying degrees of water flooding. For example, patent application CN111009666A discloses a method for preparing a double-layer microporous gas diffusion layer. In order to improve the water vapor transport capacity, a pore-forming agent is added to the raw material of one of the microporous layers to achieve a gradient change in the pore size of the microporous layer, thereby realizing the water management capability of the fuel cell. However, in double or multi-layer microporous layer structures, there will be pore size boundaries at the junctions of the multiple layers. During high-current operation, water vapor transport is fast, and water content easily accumulates at the boundaries, which is not conducive to water vapor discharge.

[0006] Patent application CN 116314905 A discloses an independent microporous layer for fuel cells and its preparation method. The method uses carbon nanotubes, hydrophobic agents, surfactants, and basic carbon materials to disperse an independent microporous layer slurry, and then uses filtration to prepare the microporous layer. This method can obtain a microporous layer structure, but the process is relatively complex, requiring dispersion and filtration. In particular, the filtration process makes it difficult to control product quality and reduces production efficiency. Furthermore, it does not rely on a carbon substrate for support, and the strength requirements for the independent microporous layer are relatively high during use.

[0007] Patent application CN102694184A introduces an independent microporous layer structure, which avoids the phenomenon of microporous layer permeation with traditional structures. However, this method requires an integrated membrane electrode, which cannot solve the problems of reuse and control. How to optimize the conductivity-drainage performance of the gas diffusion layer is of paramount importance to the development of fuel cells. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an integrated fuel cell gas diffusion layer structure and its preparation method. By adopting a unique preparation method and material combination, the microporous layer and macroporous layer are independently set in the gas diffusion layer. Thus, a conductive network is formed inside the carbon fiber without the need for high graphitization treatment of the carbon fiber paper. This meets the low internal resistance requirements of fuel cells, reduces the production cost of the fuel cell gas diffusion layer, and improves the gas diffusion efficiency, mass transfer performance and water management capability of the fuel cell. It also provides greater flexibility and convenience for the manufacturing, maintenance and performance optimization of fuel cells.

[0009] The technical solution adopted in this invention is: An integrated fuel cell gas diffusion layer structure includes a fiber skeleton and macroporous and microporous layers respectively disposed on both sides of the fiber skeleton.

[0010] Preferably, in the integrated fuel cell gas diffusion layer structure, the thickness of the fiber skeleton is 100-150 μm, the thickness of the macroporous layer is 100-150 μm, the pore size of the macroporous layer is 10-100 μm, the thickness of the microporous layer is 20-50 μm, and the pore size of the microporous layer is 50-300 nm.

[0011] A method for preparing an integrated fuel cell gas diffusion layer structure, comprising the following steps: Step S1. Prepare hydrophobic agent solution, macroporous layer slurry, and microporous layer slurry; Step S2. Immerse the fiber skeleton in a hydrophobic agent solution, then perform squeezing to control the loading, and finally dry it; Step S3. Place the fiber skeleton obtained in step S2 on the coating platform, coat one side of the macroporous layer slurry onto the fiber skeleton, and then dry it. Step S4. Coat the microporous layer slurry onto the other side of the fiber skeleton and dry it to obtain an integrated diffusion layer semi-finished product; Step S5. Heat-treat the integrated diffusion layer semi-finished product to obtain an integrated fuel cell gas diffusion layer structure.

[0012] Preferably, the method for preparing the integrated fuel cell gas diffusion layer structure includes the following steps in step S1: mixing the hydrophobic agent and deionized water at a mass ratio of 1:16-40 and mechanically stirring until fully homogeneous to obtain the hydrophobic agent solution. The hydrophobic agent is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, and ethylene-tetrafluoroethylene copolymer.

[0013] Preferably, the method for preparing the integrated fuel cell gas diffusion layer structure includes the following steps in step S1: mixing and dispersing conductive fiber material, conductive carbon material, hydrophobic agent, deionized water, and surfactant in a mass ratio of 2-7:7-2:1-3:30-50:1-3 to obtain macroporous layer slurry. The preparation of the microporous layer slurry includes the following steps: mixing and dispersing conductive fiber material, conductive carbon material, hydrophobic agent, deionized water and surfactant in a mass ratio of 2-7:7-2:5-8:30-50:1-3 to obtain the microporous layer slurry.

[0014] Preferably, in the method for preparing the integrated fuel cell gas diffusion layer structure, the conductive fiber material is selected from one or more of carbon nanotubes, carbon fibers, graphene fibers, and VGCF; the conductive carbon material is selected from one or more of carbon black, acetylene black, graphene, and graphite; the surfactant is selected from one or more of nonionic surfactants BT-9, BT12, TX100, and TW80; and the hydrophobic agent is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, and ethylene-tetrafluoroethylene copolymer.

[0015] Preferably, in the method for preparing the integrated fuel cell gas diffusion layer structure, the fiber skeleton in step S2 is carbon fiber paper with a basis weight of 10-30 g / m³. 2 The hydrophobic agent loading is 1-5%, the drying temperature is 80-100℃, and the drying time is 3-10 minutes.

[0016] Preferably, in the method for preparing the integrated fuel cell gas diffusion layer structure, the thickness of the macroporous layer slurry coating in step S3 is 100-150 μm, the thickness of the microporous layer slurry coating in step S4 is 50-100 μm, the drying temperature is 80-100℃, and the drying time is 3-10 min.

[0017] Preferably, in the method for preparing the integrated fuel cell gas diffusion layer structure, the heat treatment temperature in step S5 is 350-400℃ and the time is 30-60min.

[0018] Advantages of this invention: (1) The method for preparing the integrated fuel cell gas diffusion layer structure of the present invention involves adjusting the proportions of carbon fiber, conductive carbon black, hydrophobic agent, surfactant and pore-forming agent, dispersing them, and then coating the slurry onto carbon fiber paper using a coating method. Subsequently, the slurry is dried and sintered to form an integrated diffusion layer. The conductive network is formed inside the carbon fiber and on both sides through the form of front and back coating. The microporous layer has a uniform pore structure, which effectively improves the gas diffusion capacity of the fuel cell.

[0019] (2) The integrated fuel cell gas diffusion layer structure and its preparation method of the present invention can have a wide range of thicknesses and are relatively easy to achieve. Different thicknesses of the diffusion layer can be achieved by adjusting the wet coating thickness. Different microporous layer thicknesses can effectively adapt to different fuel cell application scenarios and operating conditions. Therefore, the integrated fuel cell gas diffusion layer structure prepared by the present invention has convenient controllability and a wide range of adaptability.

[0020] (3) The method for preparing the integrated fuel cell gas diffusion layer structure of the present invention forms a conductive network of carbon material by coating the front and back. In addition, the macroporous layer, microporous layer and support layer of the diffusion layer are seamlessly connected and there is no interface resistance, thus effectively reducing the ohmic loss during the operation of the membrane electrode.

[0021] (4) The integrated fuel cell gas diffusion layer structure and its preparation method of the present invention use carbon fiber as the skeleton and fill it with conductive carbon black and hydrophobic materials. Since there is a denser conductive carbon black material on both sides, after the internal conductive network is formed, the carbon fiber only plays a supporting role and does not need to be graphitized, thereby greatly reducing the production cost of GDL. The carbon fiber paper has a certain network structure during the production process. Although the adhesive between the fibers disappears during the heat treatment of the microporous layer, it does not change the entire original paper network. Therefore, the prepared integrated diffusion layer structure is not only low in cost and simple in process, but also has a certain strength. It is more friendly to the assembly of membrane electrode and stacking process, preventing the problem of breaking easily and low yield. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the integrated fuel cell gas diffusion layer structure of the present invention.

[0023] Figure 2 These are single-cell polarization curves for Examples 1-3 and Comparative Examples 1-4 of the present invention. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments.

[0025] Example 1 like Figure 1 An integrated fuel cell gas diffusion layer structure includes a fiber skeleton 1 and a macroporous layer 2 and a microporous layer 3 disposed on both sides of the fiber skeleton 1; the fiber skeleton 1 has a thickness of 100 μm, the macroporous layer 2 has a thickness of 100 μm and a pore size of 10 μm, the microporous layer 3 has a thickness of 20 μm and a pore size of 50 nm.

[0026] The method for preparing the integrated fuel cell gas diffusion layer structure in this embodiment includes the following steps: Step S1. Prepare hydrophobic agent solution, macroporous layer slurry, and microporous layer slurry; The preparation of the hydrophobic agent solution includes the following steps: 20g of hydrophobic agent PTFE is added to 800ml of deionized water and mixed, and mechanically stirred for 10min until fully homogeneous to obtain the hydrophobic agent solution; The preparation of the macroporous layer slurry includes the following steps: 500g of deionized water is added to 20g of BT-9 surfactant and stirred evenly. Then, 10g of PTFE emulsion is added and stirred evenly again. Finally, 70g of carbon nanotubes and 20g of carbon powder are added in sequence and dispersed for 60min to obtain the macroporous layer slurry. The preparation of the microporous layer slurry includes the following steps: 20g of BT-9 surfactant is added to 500g of deionized water and stirred evenly. Then, 50g of PTFE emulsion is added and stirred evenly again. Finally, 70g of carbon nanotubes and 20g of carbon powder are added sequentially and dispersed for 60min to obtain the microporous layer slurry. Step S2. Cut 10g carbon fiber paper into 20x20cm pieces, immerse it in a hydrophobic agent solution for 3 minutes, and finally dry it at 80℃ for 10 minutes. Step S3. Place the fiber skeleton obtained in step S2 on the coating platform, coat one side of the macroporous layer slurry with a wet coating thickness of 100 μm, and then dry it at a temperature of 80°C for 10 min. Step S4. Coat the microporous layer slurry onto the other side of the fiber skeleton, control the wet thickness to 50 μm, and dry it at 80℃ for 10 min to obtain an integrated diffusion layer semi-finished product. Step S5. The integrated diffusion layer semi-finished product is heat-treated at a temperature of 350°C for 60 minutes, and then cooled to obtain the integrated diffusion layer.

[0027] Example 2 like Figure 1 An integrated fuel cell gas diffusion layer structure includes a fiber skeleton 1 and a macroporous layer 2 and a microporous layer 3 disposed on both sides of the fiber skeleton 1; the fiber skeleton 1 has a thickness of 125 μm, the macroporous layer 2 has a thickness of 125 μm and a pore size of 10 μm, the microporous layer 3 has a thickness of 35 μm and a pore size of 50 nm.

[0028] The method for preparing the integrated fuel cell gas diffusion layer structure in this embodiment includes the following steps: Step S1. Prepare hydrophobic agent solution, macroporous layer slurry, and microporous layer slurry; The preparation of the hydrophobic agent solution includes the following steps: 20g of hydrophobic agent PTFE is added to 560ml of deionized water and mixed, and mechanically stirred for 10min until fully homogeneous to obtain the hydrophobic agent solution; The preparation of the macroporous layer slurry includes the following steps: 400g of deionized water is added to 20g of BT-9 surfactant and stirred evenly. Then, 20g of PTFE emulsion is added and stirred evenly again. Finally, 45g of carbon nanotubes and 45g of carbon powder are added in sequence and dispersed for 60min to obtain the macroporous layer slurry. The preparation of the microporous layer slurry includes the following steps: 20g of BT-9 surfactant is added to 500g of deionized water and stirred evenly. Then, 65g of PTFE emulsion is added and stirred evenly again. Finally, 45g of carbon nanotubes and 45g of carbon powder are added sequentially and dispersed for 60min to obtain the microporous layer slurry. Step S2. Cut 20g carbon fiber paper (20x20cm) and immerse it in a hydrophobic solution for 3 minutes, then dry it at 90℃ for 6 minutes. Step S3. Place the fiber skeleton obtained in step S2 on the coating platform, coat one side of the macroporous layer slurry with a wet coating thickness of 125 μm, and then dry it at a temperature of 80°C for 10 min. Step S4. Coat the microporous layer slurry onto the other side of the fiber skeleton, control the wet thickness to 75 μm, and dry it at 80°C for 10 min to obtain an integrated diffusion layer semi-finished product. Step S5. The integrated diffusion layer semi-finished product is heat-treated at a temperature of 375℃ for 45 minutes, and then cooled to obtain the integrated diffusion layer.

[0029] Example 3 like Figure 1 An integrated fuel cell gas diffusion layer structure includes a fiber skeleton 1 and a macroporous layer 2 and a microporous layer 3 disposed on both sides of the fiber skeleton 1; the fiber skeleton 1 has a thickness of 150 μm, the macroporous layer 2 has a thickness of 150 μm and a pore size of 10 μm, the microporous layer 3 has a thickness of 50 μm and a pore size of 50 nm.

[0030] The method for preparing the integrated fuel cell gas diffusion layer structure in this embodiment includes the following steps: Step S1. Prepare hydrophobic agent solution, macroporous layer slurry, and microporous layer slurry; The preparation of the hydrophobic agent solution includes the following steps: 20g of hydrophobic agent PTFE is added to 32ml of deionized water and mixed, and mechanically stirred for 10min until fully homogeneous to obtain the hydrophobic agent solution; The preparation of the macroporous layer slurry includes the following steps: 300g of deionized water is added to 20g of BT-9 surfactant and stirred evenly. Then, 30g of PTFE emulsion is added and stirred evenly again. Finally, 20g of carbon nanotubes and 70g of carbon powder are added in sequence and dispersed for 60min to obtain the macroporous layer slurry. The preparation of the microporous layer slurry includes the following steps: 20g of BT-9 surfactant is added to 300g of deionized water and stirred evenly. Then, 80g of PTFE emulsion is added and stirred evenly again. Finally, 20g of carbon nanotubes and 70g of carbon powder are added in sequence and dispersed for 60min to obtain the microporous layer slurry. Step S2. Cut 30g carbon fiber paper into 20x20cm pieces, immerse it in a hydrophobic agent solution for 3 minutes, and finally dry it at 100℃ for 3 minutes. Step S3. Place the fiber skeleton obtained in step S2 on the coating platform, coat one side of the macroporous layer slurry with a wet coating thickness of 150 μm, and then dry it at a temperature of 80°C for 10 min. Step S4. Coat the microporous layer slurry onto the other side of the fiber skeleton, control the wet thickness to 100 μm, and dry it at 80℃ for 10 min to obtain an integrated diffusion layer semi-finished product. Step S5. Heat-treat the integrated diffusion layer semi-finished product at a temperature of 400℃ for 30 minutes, and then cool to obtain the integrated diffusion layer.

[0031] Comparative Example 1 An integrated fuel cell gas diffusion layer structure includes a fiber skeleton 1 and macroporous layers 2 disposed on both sides of the fiber skeleton 1; the fiber skeleton 1 has a thickness of 100 μm, one of the macroporous layers 2 has a thickness of 100 μm and a pore size of 10 μm, and the other macroporous layer 3 has a thickness of 20 μm and a pore size of 50 nm.

[0032] A method for preparing an integrated fuel cell gas diffusion layer structure includes the following steps: Step S1. Prepare hydrophobic agent solution and macroporous layer slurry; The preparation of the hydrophobic agent solution includes the following steps: 20g of hydrophobic agent PTFE is added to 800ml of deionized water and mixed, and mechanically stirred for 10min until fully homogeneous to obtain the hydrophobic agent solution; The preparation of the macroporous layer slurry includes the following steps: 500g of deionized water is added to 20g of BT-9 surfactant and stirred evenly. Then, 10g of PTFE emulsion is added and stirred evenly again. Finally, 70g of carbon nanotubes and 20g of carbon powder are added in sequence and dispersed for 60min to obtain the macroporous layer slurry. Step S2. Cut 10g carbon fiber paper into 20x20cm pieces, immerse it in a hydrophobic agent solution for 3 minutes, and finally dry it at 80℃ for 10 minutes. Step S3. Place the fiber skeleton obtained in step S2 on the coating platform, coat one side of the macroporous layer slurry with a wet coating thickness of 100 μm, and then dry it at a temperature of 80°C for 10 min. Step S4. Coat the macroporous layer slurry to the other side of the fiber skeleton, control the wet thickness to 50 μm, and dry it at 80℃ for 10 min to obtain an integrated diffusion layer semi-finished product. Step S5. The integrated diffusion layer semi-finished product is heat-treated at a temperature of 350°C for 60 minutes, and then cooled to obtain the integrated diffusion layer.

[0033] Comparative Example 2 An integrated fuel cell gas diffusion layer structure includes a fiber skeleton 1 and macroporous layers 2 disposed on both sides of the fiber skeleton 1; the fiber skeleton 1 has a thickness of 100 μm, one of the microporous layers 2 has a thickness of 100 μm and a pore size of 10 μm, and the other microporous layer 3 has a thickness of 20 μm and a pore size of 50 nm.

[0034] A method for preparing an integrated fuel cell gas diffusion layer structure includes the following steps: Step S1. Prepare hydrophobic agent solution and microporous layer slurry; The preparation of the hydrophobic agent solution includes the following steps: 20g of hydrophobic agent PTFE is added to 800ml of deionized water and mixed, and mechanically stirred for 10min until fully homogeneous to obtain the hydrophobic agent solution; The preparation of the microporous layer slurry includes the following steps: 20g of BT-9 surfactant is added to 500g of deionized water and stirred evenly. Then, 50g of PTFE emulsion is added and stirred evenly again. Finally, 70g of carbon nanotubes and 20g of carbon powder are added sequentially and dispersed for 60min to obtain the microporous layer slurry. Step S2. Cut 10g carbon fiber paper into 20x20cm pieces, immerse it in a hydrophobic agent solution for 3 minutes, and finally dry it at 80℃ for 10 minutes. Step S3. Place the fiber skeleton obtained in step S2 on the coating platform, coat one side of the microporous layer slurry with a wet coating thickness of 100 μm, and then dry it at a temperature of 80°C for 10 min. Step S4. Coat the microporous layer slurry onto the other side of the fiber skeleton, control the wet thickness to 50 μm, and dry it at 80℃ for 10 min to obtain an integrated diffusion layer semi-finished product. Step S5. The integrated diffusion layer semi-finished product is heat-treated at a temperature of 350°C for 60 minutes, and then cooled to obtain the integrated diffusion layer.

[0035] Comparative Example 3 like Figure 1 An integrated fuel cell gas diffusion layer structure includes a fiber skeleton 1 and a macroporous layer 2 and a microporous layer 3 disposed on both sides of the fiber skeleton 1; the fiber skeleton 1 has a thickness of 100 μm, the macroporous layer 2 has a thickness of 100 μm and a pore size of 10 μm, the microporous layer 3 has a thickness of 20 μm and a pore size of 50 nm.

[0036] A method for preparing an integrated fuel cell gas diffusion layer structure includes the following steps: Step S1. Prepare hydrophobic agent solution, macroporous layer slurry, and microporous layer slurry; The preparation of the hydrophobic agent solution includes the following steps: 20g of hydrophobic agent PTFE is added to 800ml of deionized water and mixed, and mechanically stirred for 10min until fully homogeneous to obtain the hydrophobic agent solution; The preparation of the macroporous layer slurry includes the following steps: 500g of deionized water is added to 20g of BT-9 surfactant and stirred evenly. Then, 10g of PTFE emulsion is added and stirred evenly again. Finally, 70g of carbon nanotubes and 20g of carbon powder are added in sequence and dispersed for 60min to obtain the macroporous layer slurry. The preparation of the microporous layer slurry includes the following steps: 20g of BT-9 surfactant is added to 500g of deionized water and stirred evenly. Then, 10g of PTFE emulsion is added and stirred evenly again. Finally, 70g of carbon nanotubes and 20g of carbon powder are added sequentially and dispersed for 60min to obtain the microporous layer slurry. Step S2. Cut 50g carbon fibers of 20x20cm and immerse them in a hydrophobic agent solution for 3 minutes, and finally dry them at 80℃ for 10 minutes. Step S3. Place the fiber skeleton obtained in step S2 on the coating platform, coat one side of the macroporous layer slurry with a wet coating thickness of 100 μm, and then dry it at a temperature of 80°C for 10 min. Step S4. Coat the microporous layer slurry onto the other side of the fiber skeleton, control the wet thickness to 50 μm, and dry it at 80℃ for 10 min to obtain an integrated diffusion layer semi-finished product. Step S5. The integrated diffusion layer semi-finished product is heat-treated at a temperature of 350°C for 60 minutes, and then cooled to obtain the integrated diffusion layer.

[0037] Comparative Example 4 like Figure 1 An integrated fuel cell gas diffusion layer structure includes a fiber skeleton 1 and a macroporous layer 2 and a microporous layer 3 disposed on both sides of the fiber skeleton 1; the fiber skeleton 1 has a thickness of 100 μm, the macroporous layer 2 has a thickness of 100 μm and a pore size of 10 μm, the microporous layer 3 has a thickness of 20 μm and a pore size of 50 nm.

[0038] A method for preparing an integrated fuel cell gas diffusion layer structure includes the following steps: Step S1. Prepare macroporous layer slurry and microporous layer slurry; The preparation of the macroporous layer slurry includes the following steps: 500g of deionized water is added to 20g of BT-9 surfactant and stirred evenly. Then, 10g of PTFE emulsion is added and stirred evenly again. Finally, 70g of carbon nanotubes and 20g of carbon powder are added in sequence and dispersed for 60min to obtain the macroporous layer slurry. The preparation of the microporous layer slurry includes the following steps: 20g of BT-9 surfactant is added to 500g of deionized water and stirred evenly. Then, 10g of PTFE emulsion is added and stirred evenly again. Finally, 70g of carbon nanotubes and 20g of carbon powder are added sequentially and dispersed for 60min to obtain the microporous layer slurry. Step S2. Cut a 20x20cm 50g carbon fiber paper and place it on a coating platform. Coat one side of the paper with macroporous layer slurry to a wet thickness of 100μm. Then dry it at 80℃ for 10min. Step S4. Coat the microporous layer slurry onto the other side of the fiber skeleton, control the wet thickness to 50 μm, and dry it at 80℃ for 10 min to obtain an integrated diffusion layer semi-finished product. Step S5. The integrated diffusion layer semi-finished product is heat-treated at a temperature of 350°C for 60 minutes, and then cooled to obtain the integrated diffusion layer.

[0039] The monolithic diffused layer structures of Examples 1-3 and Comparative Examples 1-4 were subjected to resistance, electrochemical performance tests, and single-cell polarization tests. The test results are shown in Table 1 and Table 2. Figure 2 As shown.

[0040] Table 1

[0041] From Table 1 and Figure 2 The test results show that although the fiber skeleton in Example 1 was not graphitized to form carbon paper, its relatively loose structure allowed the filling slurry to bridge the carbon powder particles, forming a conductive network that facilitated electron transport. As shown in Table 1, the integrated diffusion layer structure of Example 1 had an internal resistance of only 10.3 mΩ. 2 This helps reduce ohmic losses during membrane electrode operation; because both sides are filled with carbon nanotubes, and with the bonding effect of PTFE, neither the macroporous layer nor the microporous layer of the slurry will easily detach. The macroporous layer provides a channel for gas transport, while the microporous layer ensures electron transport and the discharge of generated water. Figure 2 It can be seen that the membrane electrode prepared in Example 1 has excellent performance, reaching 2 A / cm. 2 @0.651V.

[0042] Although Example 2 increased the basis weight of the fiber skeleton, the slurry still permeated well due to the macroporous and microporous layers. The bridging between the carbon powders formed a conductive network, resulting in low bulk resistance and excellent electrochemical performance. As shown in Table 1, the integrated diffusion layer structure prepared in Example 1 has an internal resistance of 11.2 mΩ / cm. 2 Performance reaches 2A / cm 2 @0.65V, with the same performance as in Example 1.

[0043] The integral diffusion layer structure prepared in Example 3 has a higher bulk resistance than that of Examples 1 and 2 due to the increased basis weight and thickness of the fiber skeleton, but this does not affect its electrochemical performance.

[0044] Comparative Example 1, due to the lack of differentiation between macroporous and microporous layers, resulted in the water vapor transport channels converging during actual operation of the membrane electrode, leading to an imbalance in water vapor transport. This was particularly pronounced at high current densities. Although it exhibited a low bulk resistance, the electrochemical performance was poor due to this transport imbalance, achieving only 2 A / cm². 2 @0.627V, the flooding phenomenon is obvious; the flooding phenomenon in Comparative Example 2 is also quite obvious.

[0045] Comparative Example 3, due to its relatively dense and thick fiber skeleton, resulted in a less dense internal filling of the macroporous and microporous slurries, and a poorly formed conductive network between the toner particles, leading to a bulk resistivity of 17 mΩ / cm. 2 The corresponding ohmic loss is relatively large, and the electrochemical performance is only 2 A / cm. 2 @0.603V.

[0046] In the traditional GDL preparation process, the carbon paper is hydrophobically treated before being coated with a microporous layer to ensure good drainage performance. In Comparative Example 4, the fiber skeleton was not hydrophobically treated. During membrane electrode operation, water generated adhered to the fiber skeleton, blocking gas transport channels and causing flooding. Therefore, even with a low bulk resistivity, the electrochemical performance was poor, below 2 A / cm², due to flooding. 2 @0.6V.

[0047] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An integrated fuel cell gas diffusion layer structure, characterized in that, It includes a fiber skeleton (1) and a macroporous layer (2) and a microporous layer (3) respectively disposed on both sides of the fiber skeleton (1).

2. The integrated fuel cell gas diffusion layer structure according to claim 1, characterized in that, The fiber skeleton (1) has a thickness of 100-150 μm, the macroporous layer (2) has a thickness of 100-150 μm and a pore size of 10-100 μm, the microporous layer (3) has a thickness of 20-50 μm and a pore size of 50-300 nm.

3. A method for preparing an integrated fuel cell gas diffusion layer structure according to any one of claims 1-2, characterized in that, Includes the following steps: Step S1. Prepare hydrophobic agent solution, macroporous layer slurry, and microporous layer slurry; Step S2. Immerse the fiber skeleton in a hydrophobic agent solution, then perform squeezing to control the loading, and finally dry it; Step S3. Place the fiber skeleton obtained in step S2 on the coating platform, coat one side of the macroporous layer slurry onto the fiber skeleton, and then dry it. Step S4. Coat the microporous layer slurry onto the other side of the fiber skeleton and dry it to obtain an integrated diffusion layer semi-finished product; Step S5. Heat-treat the integrated diffusion layer semi-finished product to obtain an integrated fuel cell gas diffusion layer structure.

4. The method for preparing the integrated fuel cell gas diffusion layer structure according to claim 3, characterized in that, The preparation of the hydrophobic agent solution in step S1 specifically includes the following steps: mixing the hydrophobic agent and deionized water at a mass ratio of 1:16-40 and mechanically stirring until fully homogeneous to obtain the hydrophobic agent solution. The hydrophobic agent is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, and ethylene-tetrafluoroethylene copolymer.

5. The method for preparing the integrated fuel cell gas diffusion layer structure according to claim 3, characterized in that, The preparation of the macroporous layer slurry in step S1 specifically includes the following steps: mixing and dispersing conductive fiber material, conductive carbon material, hydrophobic agent, deionized water and surfactant in a mass ratio of 2-7:7-2:1-3:30-50:1-3 to obtain macroporous layer slurry; The preparation of the microporous layer slurry includes the following steps: mixing and dispersing conductive fiber material, conductive carbon material, hydrophobic agent, deionized water and surfactant in a mass ratio of 2-7:7-2:5-8:30-50:1-3 to obtain the microporous layer slurry.

6. The method for preparing the integrated fuel cell gas diffusion layer structure according to claim 5, characterized in that, The conductive fiber material is selected from one or more of carbon nanotubes, carbon fibers, graphene fibers, and VGCF; the conductive carbon material is selected from one or more of carbon black, acetylene black, graphene, and graphite; the surfactant is selected from one or more of nonionic surfactants BT-9, BT12, TX100, and TW80; and the hydrophobic agent is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, and ethylene-tetrafluoroethylene copolymer.

7. The method for preparing the integrated fuel cell gas diffusion layer structure according to claim 3, characterized in that, In step S2, the fiber skeleton is carbon fiber paper with a basis weight of 10-30 g / m³. 2 The hydrophobic agent loading is 1-5%, the drying temperature is 80-100℃, and the drying time is 3-10 minutes.

8. The method for preparing the integrated fuel cell gas diffusion layer structure according to claim 3, characterized in that, In step S3, the thickness of the macroporous layer slurry coating is 100-150 μm, and in step S4, the thickness of the microporous layer slurry coating is 50-100 μm. The drying temperature is 80-100℃, and the drying time is 3-10 min.

9. The method for preparing the integrated fuel cell gas diffusion layer structure according to claim 3, characterized in that, In step S5, the heat treatment temperature is 350-400℃ and the time is 30-60min.

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